1. Field of the Invention
The present invention relates to a new and improved method of charging a multiplicity of electrochemical storages, namely, cells, cell stacks, and especially batteries.
Generally speaking, the method of charging a multiplicity of storages, such as batteries, as contemplated by the present development, is of the type where, for each battery, there is at least periodically, although preferably continuously, infed and outfed aqueous electrolytic or electrolyte liquids to and from the individual anode spaces or chambers and cathode spaces or chambers the storages.
2. Discussion of the Background and Material Information
Electrical energy can be converted, with exceptionally high efficiency, into thermal energy and kinetic energy. Thus, a wide field of application is available for the employment of electrical energy in stationary systems or immobile equipment. The advantage of the ease of energy conversion, especially electrical energy into kinetic energy, in the case of mobile systems or equipment, is mitigated by the poor storage capacity of mobile energy storages or accumulators. If batteries are employed in mobile systems, such as, for example, motor vehicles, then it is desired that each electrical energy supply or storage unit possess as low weight as possible, in order to maintain as small as possible the energy expenditure needed for the transport of the storage unit or accumulator. Furthermore, in order to maximize the possible field of application, it is necessary that the stored quantity of current be optimized, in order to maximize the possible travel range of an electrically powered vehicle. For instance, this stored quantity of electrical energy should be great enough so that the vehicle can travel the distance usually travelled in one day by the vehicle, so that during those times that the vehicle is not used for travel its battery can be recharged.
In addition, as concerns many different stationary systems or consumers, it is necessary to have available a minimum amount of current or electrical energy. By providing a minimal amount of current or energy, in the event of power failure of the mains or network, further operation of the stationary energy consumers or loads can be ensued. Stationary energy storage units or accumulators are of particular interest for use, and for example, in hospitals as emergency power supplies, for emergency lighting, as electrical storages for normal operation of equipment powered by discontinuously operating energy conversion systems such as, for instance, solar energy, wind energy, tidal power plants and so forth.
These energy storages should possess as great as possible electrical potential, so that there is afforded high efficiency, and furthermore, in order to realize a particularly simple utilization thereof.
The electrical capacity of a battery is directly dependent upon the quantity of available electrolyte. In the case of a zinc-bromine battery, for instance, as described in the commonly assigned European Published Patent Application No. 0,327,528, published Aug. 9, 1989, to which reference may be readily had and the disclosure of which is incorporated herein in its entirety by reference, a circulating electrolyte system is used for increasing the quantity of electrolyte. During charging of the battery, there is separated at the cathode a zinc film which is as uniform as possible, and at the same time bromine is separated at the anode. In conjunction with a complex former provided in the aqueous electrolyte, this bromine forms a bromine complex which is exceedingly difficult to dissolve in the essentially aqueous electrolyte, so the bromine, just like the zinc, can have delivered a storage thereto. Due to the fact that the bromine complex is essentially insoluble in the aqueous phase, there is formed a suspension, and in the container or receptacle of the anode electrolyte there is separated at the floor thereof the bromine complex. The upper capacity limit of such type battery is thus defined by (1) the cathode space or chamber, and specifically, the possibility of separating the quantity of zinc, and by (2) the storage capacity of the supply vessel for the electrolyte or electrolytic liquid. The capacity or power removal, in other words, the removal or drawing of current per unit of time, is primarily dependent upon the electrode surface. The electrical potential of such battery type is dependent upon the number of cells connected in series. In order to provide as similar as possible electrochemical conditions, circulating electrolyte or electrolytic liquids are delivered to the cathode and anode spaces or chambers of a battery connected in hydraulically parallel circuits. As a result, there is afforded a uniform concentration of all constituents of the electrolyte, and furthermore, there can be obtained a uniform temperature, something which is likewise of utmost importance.
Circulating electrolyte systems bring about, on the one hand, an increase in the battery capacity, but, on the other hand, with an increase in the number of the electrodes connected in series, that is, with increasing potential, stray or vagabond currents flowing through the electrolyte liquid which, particularly in the case of greater electrical potentials, result in a continuous discharge of the battery. This battery discharge is not only present during inactive times of the battery, but also when current is drawn therefrom. In order to prevent excessive current loss, it is known to interconnect the individual electrolyte chambers or spaces by means of a conductor or line of the second order which has a resistance which varies from cell to cell. A most simple construction entails interconnecting the electrolyte chambers by a connection channel having decreasing and again increasing cross-sectional area. However, such compensation of stray currents is associated, on the one hand, with energy expenditure and, on the other hand, also with continual energy consumption even during the times of preparing the battery for functioning thereof. The currents prevailing in the battery partially cause a dissolving and renewed separation of the zinc film, so that even when storing the charged battery there can arise considerable capacity losses.
In order to prevent these unwanted currents, it has been proposed in the commonly assigned European Published Patent Application No. 0,168,377, published Jan. 15, 1986, to suppress, during the inactive times of the battery, the hydraulic connection between the individual cathode and anode spaces or chambers by using appropriate shutoff elements, such as cocks, slide valves and the like. It then is possible, during such inactive or inoperative times of the battery, to ensure that current is not internally consumed by the battery. However, it is not possible to prevent recharging within the battery or when a number of batteries are connected in series recharging between the batteries during current removal.
In order to ensure as uniform as possible charging of batteries and partial electrode stacks or packets, such can be connected in parallel for charging the same, and they can be connected in series for the removal of operating current and to maintain the electrical potential as high as possible.